So I followed the instruction and built the box. Overall everything is very square and very snug fitting.

However, I am getting this rattle sound and I am not sure where it is comingis from. Nothing in the box itself rattling. They are tight (glued, biscuit joined the all the boxes and used 8 screws to hold the inner slides aginst the outer box).

I think they are caused by air leak but I am not sure? I seem to remeber that when I was playing the speaker freeair that it made similar noise? Any idea?

It defintely is not swhoosing noise people talk about which I was told is airleak issue. This is defintely more of rattle, which sounds like it is coming from the speaker.

does the dayton have a sealed or vented pole piece, if it is vented, perhaps you got a bit of something under the dust cap. I had a very annoying noise in one of my 6 x 9s for a few days until I found a little piece of metal had fallen into the cone.

It is a Dayton Quattro 10" which has vented pole piece. However, it has mash covers on it.

I talke to Parts Express and they are telling me that I have a defective woofer. The voice coil is mis-aligned. How often does this happen?

as far as I know the speaker made rattle noise brand new, when I just hooked it up free air to an amp to test it. I thought it made funny noise, but I thought the sound will go away once I put it in the box. I think the sound is much better in the box, but it does not seem to removed that rattle sound.

Just to make sure, is your lid on tight? I used 3, 1-5/8" long drywall screws in all 4 sides in my lid to eliminate a rattle I had when I only had 4 screws. There is a LOT of pressure in the sealed chamber of this thing when you crank it up.

My top fit very tight but when tuning it in the beginning at relatively low volume the top blew of with a loud BANG ;D

Glad to hear it JB. I have to run my 8" DB below 80Hz as well. I guess "muddy" is the best description of the sound when I run it higher. My head unit has LPFs of 50, 80, and 125Hz. I think it is a 12db/octave cutoff slope. Sometimes I can run it at 80 but sure sounds "cleaner" at 50 most of the time.